Fuel feed device of engine

ABSTRACT

A fuel supply apparatus for an engine according to the present invention comprises: a plurality of injectors  13  for injecting a fuel to an intake manifold of an engine; a delivery rail  20 , to which the plurality of injectors  13  are attached, for distributing the fuel to each of the injectors  13 ; and a fuel tube  11  for feeding the fuel, which is delivered forcedly by means of a fuel pump, to the delivery rail  20 . The body portion of the delivery rail  20  has side portions having different areas, and an orifice portion wherein the end portion of the fuel tube  11  is connected to the side portion  20   a  having the largest area of the all side portions.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to a fuel supply apparatus foran engine. More specifically, the invention relates to a fuel supplyapparatus for an internal combustion engine, which is capable ofeffectively reducing the pressure pulsation of fuel while injectors forinjecting a fuel open and close.

BACKGROUND ART

A typical fuel supply apparatus for an internal combustion engine for anautomobile is designed to pump out a fuel to an injector via a fuel tubeand to inject an appropriate amount of fuel into an intake manifold ofthe engine from the injector.

Conventionally, there is widely used a return type fuel supply systemprovided with a pressure regulator for regulating the quantity of a fuelinjected from the injectors with opening and closing motion and a returntube for returning excessive fuel to a tank. In recent years, areturnless type fuel supply system requiring no return tube is put topractical use.

FIG. 6 shows a returnless type fuel supply system. In this figure,reference number 1 denotes a fuel tank. A fuel delivery rail 2 isconnected to a fuel tube 4. A plurality of injectors 5 are attached tothe fuel delivery rail 2.

In the returnless type fuel supply system of this type, it is known thatthere is a disadvantage in that a fuel pressure pulsation remarkablyoccurs in the fuel delivery pipe 2 and the fuel tube 4 every time theinjectors 5 open and close. There is a problem in that vibrations due tothe fuel pressure pulsation are transmitted as noises to the inside of acar from the underfloor of a chassis through fuel tubes. For thatreason, in order to reduce the fuel pressure pulsation, there areproposed various improvements that a damper is connected to the fueltube.

In a conventional returnless type fuel supply system, in order to reducethe fuel pressure pulsation, the fuel tube includes the damper fordamping the pulsation. In addition, Japanese Patent Laid-Open No.1999-2164 discloses a technique wherein a delivery rail having a bodyformed of a pressed sheet metal of 0.8 mm or more in thickness, and therigidity and content volume of the delivery rail are set inpredetermined ranges so that the pulsation resonance cycle of a fuelpiping system is an idling cycle or less, thereby reducing the fuelpressure pulsation.

In the prior art disclosed in the above described Japanese PatentLaid-Open No. 1999-2164, although there is an advantage in that it isnot required to use any dampers, it is required to increase the volumeof the fuel piping system in order to reduce the pulsation.

However, there are some cases where it is difficult to increase thevolume of the fuel piping system in a very narrow limited space forengine room in order to only reduce the fuel pressure pulsation. Inaddition, this is not a reasonable countermeasure against reducing thefuel pressure pulsation.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to eliminate theabove described problems in the prior art and to provide a fuel supplyapparatus for an engine, which is capable of effectively reducing thefuel pressure pulsation occurred by the injectors opening and closing,by using an inexpensive means and without increasing the volume of afuel piping system.

In order to accomplish this object, there is provided a fuel supplyapparatus for an engine for supplying a fuel, which is pumped out bymeans of a pump from a fuel tank to an engine, said fuel supplyapparatus comprises a plurality of injectors for injecting the fuel toan intake manifold of the engine; a delivery rail, to which theplurality of injectors are attached, for distributing the fuel to eachof the injectors; and a fuel tube for introducing the fuel, which isdelivered forcedly by means of said pump, to the delivery rail, whereina body portion of the delivery rail has side portions having differentareas, and an orifice portion which is open on the largest side portionof the all side portions and to which an end portion of the fuel tube isconnected.

According to the present invention, it is possible to effectively reducethe fuel pressure pulsation in the fuel tube by the injectors openingand closing, by an inexpensive tube or the like and without increasingthe volume of a fuel piping system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the first preferred embodiment of afuel supply apparatus for an engine according to the present invention;

FIG. 2 is a cross-sectional view taken along line II—II of FIG. 1;

FIG. 3 is a sectional view showing a modified example of the firstpreferred embodiment of a fuel supply apparatus for an engine accordingto the present invention;

FIG. 4 is a perspective view showing the second preferred embodiment ofa fuel supply apparatus for an engine according to the presentinvention;

FIG. 5 is a sectional view of a muffler pipe in the preferred embodimentshown in FIG. 4; and

FIG. 6 is an illustration for explaining a conventional fuel returnlesssupply system for an engine.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the accompanying drawings, the preferred embodiment of afuel supply apparatus for an engine according to the present inventionwill be described below.

First Preferred Embodiment

FIG. 1 is a view showing the first preferred embodiment of a fuel supplyapparatus for an engine according to the present invention. Referencenumber 20 denotes a delivery rail, and reference number 11 denotes afuel tube. The delivery rail 20 and the fuel tube 11 constitute areturnless fuel supply system. A fuel in a fuel tank (not shown) isdischarged from a pump to be pumped out forcedly to the delivery rail 20via the fuel tube 11. The body portion of the delivery rail 20 comprisesa shape tube having an L-shaped cross section. A plurality of injectors13 are attached to the body portion of the delivery rail 20 so as to bearranged in longitudinal directions. The injectors 13 are inserted intoan intake manifold of an engine (not shown).

FIG. 2 is a cross-sectional view of the delivery rail 20. The bodyportion of the delivery pipe 20 comprises an upper case 21 a and a lowercase 21 b which are formed of a sheet metal through a process of pressworking. These cases are put together by brazing or welding to form ashape tube having a cross-sectional shape formed by combining at leasttwo rectangles, i.e., a shape tube having an L-shaped cross section inthis preferred embodiment.

Since the delivery rail 20 thus forms the shape tube having the L-shapedcross section, the lengths of the respective side portions forming thecross section are different, so that the areas of six side portions aredifferent. The end portion of the fuel tube 11 is connected to thelargest upper side portion 20 a of the six side portions. The sideportion 20 a have an orifice portion 22 opened with a diameter d. Inthis embodiment, the thickness of the delivery rail 20 is preferablyabout 0.7 mm in order to add a pulsation damping function and rigidity.The connected position of the fuel tube 11 is preferably substantiallythe center of the upper side portion 20 a. Furthermore, the injectors 13are attached to the lower side portion 20 b.

With this construction, the advantageous function of the first preferredembodiment will be described below.

When the fuel discharged from a pump (not shown) flows through the fueltube 11 to be fed into the delivery rail 20, the fuel is distributedinto the respective injectors 13 from the delivery rail 20. The openingand closing operations of each of the injectors 13 are controlled by acontrol unit (not shown) in timing according to the operating conditionsof the engine. That is, when the injector 13 is open, the fuel isinjected from the injector 13 while it is open, and when the injector 13is closed, the injection of the fuel is suspended. Since this fuelsupply apparatus adopts the returnless system wherein any return tubesfor returning the fuel to the tank are not provided, the fuel pressurepulsation is caused in the fuel tube 11 by the opening and closingrepeated motions of the injectors 13.

According to the first preferred embodiment of the present invention,since the delivery pipe 20 comprises the shape tube having the L-shapedcross section, the ratio (A/a) of the area (A) of the upper side portion20 a to the area (a) of the orifice portion 22 can be increased withoutchanging the volume of the delivery rail 20 itself by providing theorifice portion 22 in the largest upper side portion 20 a to connect thefuel tube 11 to the orifice portion 22. This orifice portion 22 servesas a fuel inlet as well as an orifice for preventing the pressurepulsation caused by the injectors 13 opening and closing fromtransmitting to the fuel tube 11. Thus, as described above, the arearatio of the upper face portion 20 a to the orifice portion 22, i.e.,the orifice ratio (A/a), can be increased (to preferably 46 or more), sothat the orifice effect is increased to more effectively suppress thepropagation of pulsation toward the fuel tube of the vehicular body. Inaddition, since the orifice ratio can be greatly increased withoutincreasing the volume of the delivery rail 20 itself, this isadvantageous to the installation space for the delivery rail 20.Moreover, the orifice ratio can be increased without decreasing theorifice diameter d of the orifice portion 22, thus, without increasingthe pressure loss.

Furthermore, while the fuel tube 11 is most preferably connected to thecentral portion of the upper side portion 20 from the standpoint of theorifice effect, the present invention should not be limited thereto.From the standpoint of the orifice effect, there is an advantage if thefuel tube 11 is connected to the largest side, so that thecross-sectional shape of the delivery rail 20 should not be limited tothe L-shaped cross section. For example, as shown in FIG. 3, the bodyportion of the delivery pipe rail 20 may comprise a shape tube having aC-shaped cross section, and the orifice portion 22 may be provided inthe central portion of the largest side portion 30 to be connected tothe end portion of the fuel tube. Thus, it is possible to obtain thesame effects.

Second Preferred Embodiment

FIG. 4 shows a second preferred embodiment of a fuel supply apparatusaccording to the present invention.

In this preferred embodiment, the body portion of the delivery rail 20is the same as that in FIG. 1.

A muffler tube 14 is provided in the midway along the fuel tube 11. Asshown in FIG. 5, the muffler tube 14 comprises a tube body formed bybrazing a cylindrical pipe 15 and a tapered pipe 16 together. And anexpansion chamber 17 is formed in the muffler pipe 14.

As the cylindrical member 15, a metal thin tube, e.g., a metal tubehaving a thickness of 0.7 mm or less, which has a large diametersufficient to form the expansion chamber 17 therein, is used. Thetapered tube 16 forms a conical outlet passage 16 a, the diameter ofwhich decreases toward downstream.

The operation of the second preferred embodiment of a fuel supplyapparatus according to the present invention will be described below.

Since the thickness of the cylindrical member 15 forming the expansionchamber 17 of the muffler tube 14 is small, the cylindrical member 15 isdeformed to damp the fuel pressure pulsation if the pressure varies dueto the pulsation. In order to maintain the rigidity of the cylindricalmember 15 and ensure the deformation property for damping the pulsation,the thickness of the cylindrical member 15 is about 0.7 mm. Thus, theoccurring pulsation is effectively reduced by the reactive silencereffect of such a muffler tube 14. In addition, while the fuel is fed tothe engine, the pressure loss can be reduced by forming the outlet sidepassage 16 a of the muffler tube 14. On the other hand, the inlet sidepassage 16 b of the muffler exhibits the orifice effect, so that it isalso possible to prevent the propagation of the pulsation toward thevehicular body.

In addition, by combining such a muffler tube 14 with the delivery rail20, the propagation of pulsation to the fuel tube 11 is suppressed bythe orifice effect of the delivery rail 20, and the pulsation returningto the fuel tube 11 by the reactive silencer effect of the muffler tube14 is further damped, so that the pulsation can be more effectivelyreduced.

What is claimed is:
 1. A fuel supply apparatus for an engine forsupplying a fuel, which is pumped out by means of a pump from a fueltank to an engine, said fuel supply apparatus comprising: a plurality ofinjectors for injecting the fuel to an intake manifold of the engine; adelivery rail, to which the plurality of injectors are attached, fordistributing the fuel to each of the injectors; and a fuel tube forintroducing the fuel, which is delivered forcedly by means of said pump,to the delivery rail, wherein a body portion of the delivery rail hasside portions having different areas, and an orifice portion which isopen on the largest side portion of the all side portions and to whichan end portion of the fuel tube is connected.
 2. A fuel supply apparatusaccording to claim 1, wherein the body portion of the delivery railcomprises a shape tube having a cross section having unequal sides.
 3. Afuel supply apparatus according to claim 2, wherein the body portion ofthe delivery pipe comprises a shape tube having a cross-sectional shapewhich is formed by combining at least two rectangles.
 4. A fuel supplyapparatus for an engine according to claim 2, wherein the body portionof the delivery rail comprises a shape tube having an L-shaped crosssection.
 5. A fuel supply apparatus according to claim 2, wherein thebody portion of the delivery rail comprises a shape tube having aC-shaped cross section.
 6. A fuel supply apparatus according to claim 1,wherein the orifice portion is substantially formed in the centralportion of the largest side portion.
 7. A fuel supply apparatusaccording to claim 6, wherein the thickness of the side portion, inwhich the orifice is formed, is 0.7 mm or less.
 8. A fuel supplyapparatus according to claim 1, which further comprises a thincylindrical muffler tube member which is provided in the fuel tubeupstream of the delivery rail and which has an expansion chambertherein.
 9. A fuel supply apparatus according to claim 8, wherein themuffler tube member is formed by connecting a thin cylindrical member toa tapered tube member, the diameter of which decreases towarddownstream.
 10. A fuel supply apparatus according to claim 9, whereinthe thin cylindrical member of the muffler tube member is a metal tubehaving a thickness of 0.7 mm or less.